1. Field of the Invention
The present invention relates to a proximity type exposure apparatus, and particularly, to a proximity type exposure apparatus provided with a load support unit supporting a mask stage and a guide unit driving the mask stage and to a method of aligning a mask to a substrate using the proximity type exposure apparatus.
2. Description of the Related Art
A process of forming a plurality of thin films is required in a manufacturing process of a semiconductor device or a liquid crystal display (LCD) device, and the thin film forming process is performed by a common exposure technology. Here, the exposure technology is that ultraviolet rays or X-rays are radiated through a mask having a predetermined pattern to expose a photosensitive material applied on a substrate and therefore, the predetermined pattern is transferred onto the substrate.
As for the LCD device, the exposure technology is used in many processes such as patterning of a gate line, a data line and a unit pixel of the LCD device and forming of a color filter layer of a color filter substrate. For this reason, the technology is considered to be important since transferring of a precise pattern on the substrate is needed.
In general, an exposure apparatus can be categorized into a projection type exposure apparatus allowing a reduced and magnified pattern transfer and a proximity type exposure apparatus allowing pattern transfer at a 1:1 ratio by using horizontal and parallel rays of light.
The projection type exposure apparatus that allows exposure with a reduced pattern can be commonly used to fabricate a device that requires integration such as a semiconductor device. When the same size pattern needs to be formed on a large area, for example, for an LCD device, the proximity type exposure apparatus using a large mask is suitable.
The proximity type exposure apparatus needs to perform exposure on a substrate, approaching the substrate as close as possible in order to transfer a mask pattern onto the substrate completely. There is a contact type exposure apparatus that performs exposure in a state that a mask is in complete contact with the substrate. However, such an exposure apparatus may cause damage to the mask by a foreign substance on the substrate or the contact itself between the mask and the substrate. Therefore, the proximity type exposure apparatus is directed to making a mask stage close to the substrate without any contact therebetween.
Each of the proximity type and projection type exposure apparatuses basically includes an illumination optical system generating light for exposure, a mask stage supporting a mask having a predetermined pattern, a substrate support chuck on which a substrate onto which the pattern of the mask is transferred is mounted, and supporters equipped with the substrate support chuck.
Also, because it is important for the exposure apparatus to precisely transfer a pattern of a mask onto a substrate, a plurality of alignment cameras for checking locations of the mask stage and the substrate are provided for the purpose of aligning the mask stage and the substrate. The alignment camera recognizes an alignment key that may be formed on the substrate support chuck or the substrate, thereby aligning the substrate and the mask stage.
As an LCD device gets larger, a mask becomes larger and a mask stage that supports the mask also becomes larger. The mask is installed under the mask stage so that the mask can approach the substrate as close as possible, and the mask is fixed to the mask stage by a fixing member.
The proximity type exposure apparatus having the aforementioned elements according to a related art will now be described with reference to FIG. 1.
Referring to FIG. 1, the proximity type exposure apparatus includes an illumination optical system 101 providing light, a mask stage 105 installed under the illumination optical system 101 and supporting a mask 110, supporters 120 supporting four corners of the mask stage 105, an x-axis driving plate 113 and a y-axis driving plate 112 formed under the mask stage 105 and supporting a substrate 114, a chuck 111 supporting the x-axis driving plate 113 and the y-axis driving plate 112, and a base plate 150 constituting a base of the exposure device.
The illumination optical system 101 serves to transfer a mask pattern onto the substrate 114 by generating light such as ultraviolet rays or x-rays.
The mask stage 105 includes an upper plate 103 directly coupled with the mask 110 and a lower plate 102 supporting the upper plate 103 of the mask stage and constituting a base of the mask plate.
The mask stage 105 supports the mask 110 such that the upper plate 103 on which the mask is directly arranged is coupled under the lower plate 102 to allow the mask 110 to approach the substrate 114 as close as possible. Also, the lower plate 102 and the upper plate 103 of the mask stage are vacant in the middle so as to allow light proceeding from the illumination optical system 101 to pass through the mask 110 and be emitted to the substrate 114.
Also, four corners of the mask stage 105 are supported by the bar-shaped mask stage supporters 120.
Under the mask stage 105 the substrate 114 is arranged and the x-axis driving plate 113 and the y-axis driving plate 112 for moving the substrate 114 are installed.
The y-axis driving plate 112 is installed on the support chuck 111. A predetermined rail is installed in the y-axis direction on the support chuck 111, and the y-axis driving plate 112 is coupled to the rail, so that the substrate can be moved in the y-axis direction. Also, a predetermined rail is also installed on the y-axis driving plate 112 and the x-axis plate 113 is coupled to the rail, so that the substrate can be moved in the x-axis direction.
The substrate 114 is mounted on the x-axis plate 113 and is moved to a certain coordinate by the operation of the x-axis driving plate 113 and the y-axis driving plate 112. Because the substrate 114 is greater than the mask in general, a plurality of exposure processes are performed while the substrate 114 moves. In such a manner, a mask pattern is transferred onto the entire substrate 114.
It is very important for the exposure apparatus to accurately align a mask stage and a substrate because the apparatus is directed to transferring a fine mask pattern onto a substrate. Therefore, in order to precisely align the mask stage and the substrate, an alignment camera (not shown) for the alignment between the substrate and the mask stage is installed on the mask stage, and an alignment key is installed on the substrate or the x-axis driving plate.
The alignment camera precisely aligns the substrate and the mask stage by checking the alignment key.
However, because the x-axis driving plate 113 and the y-axis driving plate 112 are used to move the substrate to align the substrate and the mask stage, a limitation exists in that the mask and the substrate are not or cannot easily be aligned with precision, which is a problem since the mask and the substrate should be aligned by the unit of micrometer or smaller.